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Extreme weather could become norm around Indian Ocean

By Michael Slezak

EXTREME weather around the Indian Ocean will become the norm if nothing is done to stem global warming. That’s the upshot of the first study to model the future state of the Indian Ocean’s version of El Niño.

The Indian Ocean Dipole (IOD) is an oscillation of warm water across the equator, similar to El Niño in the Pacific. Both have a major influence on regional weather patterns. During the IOD’s positive phase, sea surface temperatures rise in the Arabian Sea and fall around Indonesia, changes which reverse in the negative phase. Rainfall follows the warm water, says Wenju Cai of CSIRO, Australia’s national research agency in Melbourne.

Crucially, the models allowed them to forecast how the IOD might behave in decades to come. The team found that most of the time, the positive phase is dampened by wind. This reduces the temperature difference across the Indian Ocean. But all 54 climate models the team examined predicted that this wind will weaken as the world warms. As a result, the dipole will tend to get stuck in the positive direction, bringing rain to Africa that would otherwise have fallen on Australia and Indonesia (Nature Geoscience, doi.org/p9w).

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The models suggest that if the world keeps burning fossil fuels and does little to prevent climate change – the trajectory we are on – extreme events like Australia’s drought will be commonplace by 2050. By 2100, they will be considered mild. Cai says the definitions of the phases will need to change to reflect the new normal.

This article appeared in print under the headline “Weather will get nasty as El Niño sibling acts up”